Joan Casey, a postdoctoral researcher at the UC Berkeley School of Public Health, led the research team that examined the relationship between increased seismic activity in Oklahoma since 2010 and anxiety. The team compared earthquake data with Google search-engine data related to anxiety—and found a direct relationship between the two.

In other words, more earthquakes means more people going to Google for help with their anxiety.

Google data served as the tool for Casey and her team to look into the week-by-week mental health of their population survey. “Any population surveys we have right now are generally available at the annual level, but these earthquakes were occuring every week potentially,” Casey said. “We wanted to find a finer-grained estimate of mental health.”

The data could also give a more immediate, relatively unfiltered look at the affected population. “People turn to Google to ask questions that you might not ask someone else, or if they’re not yet ready to talk to a healthcare provider,” Casey said. “[Google] could be this subclinical threshold.”

As the study shows, earthquakes in Oklahoma have steadily increased alongside fracking in the state. According to the 2015 U.S. Geological Survey, Oklahoma now sees more regular earthquakes than California. And scientists have pointed to wastewater injection as the culprit, which, as this study cites, has contributed to 98 percent of earthquakes in the central and eastern United States in the last decade. This part of the fracking process pumps disposal fluid deep underground, altering pressure in geological faults and spurring earthquakes in areas naturally less prone to seismicity.

Aside from possible environmental and economic impacts of such earthquakes, this study points to the often unseen effects on population psychology where these earthquakes occur.

"It does appear that the population of Oklahoma is reacting to these earthquakes,” Casey told Environmental Health News. “And that might be something policy makers and others will want to take into account when deciding how to move forward with fracking in the state and how to move forward with the safe wastewater reinjection if they continue with the practice.”

Coauthors of the study included Sidra Goldman-Mellor, assistant professor, public health at UC Merced and Ralph Catalano, professor emeritus, UC Berkeley School of Public Health.